The Obama administration Tuesday reversed itself and said it would not veto a major 2012 defense bill that expands the American military’s authority to arrest suspected terrorists anywhere in the world—including Americans on U.S. soil—and hold them indefinitely without charge or the right to a civilian trial.

“We have concluded that the [defense bill’s] language does not challenge or constrain the President’s ability to collect intelligence, incapacitate dangerous terrorists, and protect the American people,” Press Secretary Jay Carney said in a written statement. “The President’s senior advisers will not recommend a veto.”

Only two weeks ago Carney told reporters that Obama stood by his veto threat. The reversal by the White House will now subject the president to an unprecedented lobbying campaign by retired generals, intelligence officers, and myriad civil rights organizations to reject the 2012 National Defense Authorization Act.

“If President Obama signs this bill, it will damage both his legacy and American’s reputation for upholding the rule of law,” said Laura W. Murphy, director of the ACLU Washington Legislative Office. “The last time Congress passed indefinite detention legislation was during the McCarthy era and President Truman had the courage to veto that bill. We hope that the president will consider the long view of history before codifying indefinite detention without charge or trial.”

The 1,844-page conference committee report was passed by the House 283-136 on Wednesday night and now goes to the Senate where an earlier version passed 93-7. While dealing with innumerable aspects of military policy, its counterterrorism section states that the entire world, including American soil, is a battlefield in the war on terror. It expands the U.S. military’s authority to arrest and indefinitely detain anyone, even citizens, suspected of aiding terrorists.

“This is a worldwide authority provision,” said Christopher Anders, the ACLU’s senior legislative counsel. “No corner of the world is off limits… With United States citizens, the hope would be that there would be constitutional protections that would apply. But that kind of challenge is still very uncertain under U.S. law, and it would take years [for such litigation] to work its way through the courts.

In a press briefing earlier this week, Anders and top attorneys from Human Rights First, Human Rights Watch, and the National Security Network explained the implications of the defense policy bill heading toward President Obama’s desk. The legislation does not fund troops fighting in America’s overseas conflicts; that is another bill also heading to his desk.

In sum, the very policies that candidate Obama pledged to end by closing the military’s prison at Guantanamo Bay, Cuba, he is now not only supporting, but expanding onto U.S. soil, the civil rights lawyers said. Besides giving the military authority for indefinite detention without trying suspects, the bill would require military detention for many terrorism suspects. And it would all but ban transferring any exonerated prisoners from Guantanamo, where 88 of the 171 prisoners held there have been cleared of terrorist involvement.

“It would, if enacted into law, significantly change the way the U.S. approaches detentions in a so-called ‘law of war’ context,” Andrea Parsow of Human Rights Watch said, concluding it would lead to the expansion of Guantanamo, not its closure. The legislation envisions the military’s role in current and future conflicts.

Other experts, such as Heather Hurlburt, National Security Network executive director, said no one in senior national security or domestic law enforcement positions—including the FBI director, CIA director, National Intelligence director, and Secretary of Defense—wanted the military detention authority in the bill, and national security officials repeatedly told Senate and House Armed Services Committee members that the provisions were unworkable.

“The national security establishment comprehensively rejects these provisions as representing the militarization of our justice system,” she said, noting that on Monday the New York Times had an unprecedented op-ed co-written by Charles Krulak and Joseph Hoar, both retired four-star Marine generals, calling for a presidential veto. They said that inserting military forces into domestic anti-terror operations would vastly complicate law enforcement, undermine constitutional rights and boost Al Qaeda’s recruiting.

Hurlburt pointed out that the Senate and House Armed Service Committee chairs could not even agree on what the military detention provisions would mean, with the House chair saying it was a dramatic expansion of domestic military authority, and the Senate chair saying it was not. That scenario would lead to the Supreme Court having to clarify the legislation’s intent and defense policy sometime in the future, she said.

Consider the case of a Nigerian man, the so-called underwear bomber, arrested last Christmas Eve in Michigan after he failed to detonate a bomb on an airline flight from Amsterdam. Under the law, Hurlburt said, the FBI or local law enforcement would have to turn him over to the military, even though there is no military prison in Michigan. The White House would have to approve a waiver in order for a terror suspect not to be held by the military, which is an unduly complicated procedure. Interrogation time would be lost, Hurlburt said, explaining why so many senior law enforcement and military officials oppose the provision.

None of those arguments, however, are new to Senate or House members who support the expanded military detention powers. After intense debate in the Senate, where all amendments to remove or change the detention provisions failed, the House did not change a single word, the ACLU’s Anders said. Instead it added murky language saying that nothing in the law was intended to interfere with domestic law enforcement.

The White House’s statement saying it would not veto the law ignored these concerns, even as the FBI director again warned senators on Wednesday about the military detention provisions.

“While we remain concerned about the uncertainty that this law will create for our counterterrorism professionals,” Carney’s statement said, “the most recent changes give the President additional discretion in determining how the law will be implemented, consistent with our values and the rule of law, which are at the heart of our country’s strength.”